Electronic sphygmomanometer

ABSTRACT

In an electronic sphygmomanometer, a protruding member is provided in an outside surface of a first air port connection head, and when a first air port is pushed into the first air port connection head, the protruding member passes over a first shielding plate while elastically deforming and reaches a position on the inner side of the first shielding plate. As a result, the first air port connection head is prevented from pulling out from the first air port, and a sense of the protruding member locking in upon returning to its original form is imparted on a worker. It is therefore possible to provide an electronic sphygmomanometer that includes, as a structure in which a pressure sensor used in the electronic sphygmomanometer is disposed, a peripheral structure for the pressure sensor that can improve the reliability of blood pressure measurement values.

TECHNICAL FIELD

This invention relates to electronic sphygmomanometers, and particularlyrelates to electronic sphygmomanometers that improve the reliability ofblood pressure measurement values.

BACKGROUND ART

Blood pressure is one index for analyzing cardiovascular disease.Performing a risk analysis for cardiovascular disease based on bloodpressure is effective in preventing cardiovascular-related conditionssuch as stroke, heart failure, and myocardial infarction. In particular,morning hypertension, in which the blood pressure rises in the earlymorning, is related to heart disease, stroke, and the like. Furthermore,among morning hypertension symptoms, the symptom called “morning surge”,in which the blood pressure rapidly rises within one hour to one and ahalf hours after waking up, has been found to have a causal relationshipwith stroke. Accordingly, understanding the interrelationship betweentime (lifestyle) and changes in blood pressure is useful in riskanalysis for cardiovascular-related conditions. It is thereforenecessary to continuously measure blood pressure over a long period oftime.

Furthermore, recent study results have shown that home blood pressure,which is blood pressure measured at home, is more effective in theprevention, diagnosis, treatment, and so on of cardiovascular-relatedconditions than blood pressure measured at a hospital or during a healthexamination (casual blood pressure). Accordingly, sphygmomanometers forhome use have become widely prevalent, and home blood pressure valueshave started to become used in diagnoses.

In order to improve the measurement precision of sphygmomanometers, JPH7-51233A (called “Patent Literature 1” hereinafter) discloses aninvention in which processing for correcting error in a measurementvalue that is dependent on the characteristics of the pressure sensorfor blood pressure measurement is performed in the production stage ofthe electronic sphygmomanometer.

JP H2-19133A (called “Patent Literature 2” hereinafter) and U.S. Pat.No. 7,594,892 (called “Patent Literature 3” hereinafter) disclosetechniques for improving the reliability of blood pressure measurementvalues using two pressure sensors.

According to the electronic sphygmomanometer disclosed in PatentLiterature 1, the correction regarding the pressure sensor is performedbased on differences in the characteristics of the individualselectronic sphygmomanometers in the electronic sphygmomanometerproduction stage; however, unlike a sphygmomanometer used in a medicalfacility such as a hospital, a sphygmomanometer for home use isgenerally not periodically corrected after purchase, except for incertain situations such as a malfunction.

For example, even if the pressure sensor output, which is of utmostimportance in blood pressure measurement, deviates beyond a specifiedtolerance margin, there is no way to know that this has happened, andtherefore it is not clear whether blood pressure measurement values arecorrect. For this reason, even if there is a large difference between ablood pressure measurement value and the normal blood pressuremeasurement value or the casual blood pressure measurement value, it isnot clear whether the blood pressure values are actually different, orthe blood pressure values are different due to error in the pressuresensor of the sphygmomanometer, thus causing concern on the part of theuser.

Meanwhile, some sphygmomanometers for medical facilities include twopressure sensors, and pressure is monitored based on the output of thesepressure sensors. However, the functions of these two pressure sensorsare used for different purposes in such sphygmomanometers. That is, theblood pressure is calculated using cuff pressure information obtained byone of the pressure sensors, and abnormality detection is performedbased on the output of the other pressure sensor.

Specifically, an abnormality is detected if the pressure value detectedby the pressure sensor greatly exceeds 300 mmHg, for example. In thiscase, safety is ensured by stopping the pump and releasing the valve.Accordingly, the other pressure sensor is applied as a safety measurespecified in the Japanese medical standard IEC 60601-2-30, and does notguarantee the precision of the one pressure sensor used for bloodpressure measurement.

In light of this, it is necessary for the precision of the one pressuresensor, which is used for detecting blood pressures, to be guaranteed bythat pressure sensor itself. There is thus a demand for a high-precisionpressure sensor that is not influenced by external disturbances such astemperature changes, that changes little over time, and that isinexpensive. Furthermore, providing two pressure sensors that performdifferent functions means that the malfunction rate of thesphygmomanometer due to malfunctions in the pressure sensors will simplybe double the malfunction rate of a sphygmomanometer that has only onepressure sensor.

Meanwhile, a pressure sensor used in an electronic sphygmomanometermeasures pressures of fluids, liquids, and so on using apressure-sensitive element via a diaphragm (a stainless steel diaphragm,a silicon diaphragm, or the like), converts the measurement into anelectric signal, and outputs the signal.

For example, in the case of a diffused piezoresistive semiconductorpressure sensor, a semiconductor strain gauge is provided on the surfaceof the diaphragm, and a change in electrical resistance caused by apiezoresistance effect occurring when the diaphragm deforms due to anoutside force (a pressure) is converted into an electric signal.

Meanwhile, with an electrostatic capacitance pressure sensor, acapacitor is formed by opposing a glass fixed electrode and a siliconmobile electrode, and a change in electrostatic capacitance producedwhen the mobile electrode deforms due to an outside force (a pressure)is converted into an electric signal.

The reliability of blood pressure measurement values is maintainedbecause only an outside force (a pressure) that is to be measured isapplied to the pressure sensor. However, because the amount ofdeformation in the diaphragm, the amount of deformation in the mobileelectrode, and so on are on the order of microns, such pressure sensorsare extremely susceptible to extraneous outside stress, and it istherefore necessary to carefully consider the peripheral structure ofthe pressure sensor. Specific peripheral structures for a pressuresensor, however, are neither disclosed nor considered in PatentLiterature 1 through 3.

CITATION LIST Patent Literature

Patent Literature 1: JP-H7-51233A

Patent Literature 2: JP-H2-19133A

Patent Literature 3: U.S. Pat. No. 7,594,892

SUMMARY OF INVENTION

Embodiments of the present invention consider specific peripheralstructures for pressure sensors. Therefore, one or more embodiments ofthe present invention provide an electronic sphygmomanometer thatincludes, as a structure in which a pressure sensor used in theelectronic sphygmomanometer is disposed, a peripheral structure for thepressure sensor that can improve the reliability of blood pressuremeasurement values.

An electronic sphygmomanometer according to one or more embodiments ofthis invention includes: a cuff that is worn on a measurement area; aninflation and deflation unit that adjusts a pressure applied to thecuff; a pressure detecting unit, having a pressure sensor, for detectinga cuff pressure within the cuff based on pressure information outputtedfrom the pressure sensor; and a blood pressure calculation unit thatcalculates a blood pressure based on a change in the cuff pressuredetected by the pressure detecting unit.

The pressure sensor is disposed upon a first main surface of an internalcircuit board; the pressure sensor has an air port that protrudes on asecond main surface that is on the opposite side of the internal circuitboard as the first main surface; a pressure sensor air tube is connectedto the air port; and a branching air tube that branches from a cuff airtube connected to the cuff is connected to the pressure sensor air tube.

The pressure sensor air tube has an air port connection head connectedto the air port; and an engagement region that engages the air portconnection head with the internal circuit board is provided between theair port connection head and the internal circuit board.

In the electronic sphygmomanometer according to or more embodiments ofthe present invention, the internal circuit board has a shielding platethat is disposed a predetermined distance from the second main surfaceand in which is provided an opening that exposes the air port on theside of the second main surface; and the air port connection head has aprotruding member, serving as the engagement region, that engages withan inner surface side of the shielding plate at the opening when theoutside surface of the air port connection head is connected to the airport.

In the electronic sphygmomanometer according to one or more embodimentsof the present invention, a first pressure sensor and a second pressuresensor are provided as the pressure sensors; the pressure detecting unitdetects the cuff pressure within the cuff based on the pressureinformation outputted from the first pressure sensor and the secondpressure sensor; a first air port for the first pressure sensor and asecond air port for the second pressure sensor are provided as the airport; the internal circuit board has a first shielding plate that isdisposed a predetermined distance from the second main surface and inwhich is provided a first opening that exposes the first air port on theside of the second main surface, and a second shielding plate that isdisposed a predetermined distance from the second main surface and inwhich is provided a second opening that exposes the second air port onthe side of the second main surface; the pressure sensor air tube has afirst air port connection head connected to the first air port and asecond air port connection head connected to the second air port; thefirst air port connection head has the protruding member that engageswith an inner surface side of the first shielding plate at the firstopening when the outside surface of the first air port connection headis connected to the first air port; and the second air port connectionhead has the protruding member that engages with an inner surface sideof the second shielding plate at the second opening when the outsidesurface of the second air port connection head is connected to thesecond air port.

In the electronic sphygmomanometer according to one or more embodimentsof the present invention, no less than two of the protruding members areprovided in the outside surface of the air port connection head.

In the electronic sphygmomanometer according to one or more embodimentsof this invention, it is possible to provide an electronicsphygmomanometer including a structure for disposing a pressure sensorthat can improve the reliability of blood pressure measurement values.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of the outside of an electronicsphygmomanometer according to an embodiment.

FIG. 2 is a diagram illustrating a hardware configuration of theelectronic sphygmomanometer according to the embodiment.

FIG. 3 is a diagram illustrating a functional configuration of theelectronic sphygmomanometer according to the embodiment.

FIG. 4 is a flowchart illustrating a blood pressure measurement processaccording to the embodiment.

FIG. 5 is a perspective view illustrating the internal structure of theelectronic sphygmomanometer according to the embodiment, where a frontcover has been removed.

FIG. 6 is a first diagram illustrating a structure in which an internalcircuit board and two pressure sensors used in the electronicsphygmomanometer according to the embodiment are viewed from the rearside of the internal circuit board.

FIG. 7 is a second diagram illustrating a structure in which an internalcircuit board and two pressure sensors used in the electronicsphygmomanometer according to the embodiment are viewed from the rearside of the internal circuit board.

FIG. 8 is a cross-sectional view illustrating the structure of an airtube used in the electronic sphygmomanometer according to theembodiment.

FIG. 9 is a perspective view illustrating the external appearance of theair tube used in the electronic sphygmomanometer according to theembodiment.

FIG. 10 is a cross-sectional view taken along the X-X line in FIG. 9.

FIG. 11 is a cross-sectional view corresponding to the X-X line in FIG.9, illustrating another structure of an air tube used in the electronicsphygmomanometer according to the embodiment.

FIG. 12 is a cross-sectional view corresponding to the X-X line in FIG.9, illustrating yet another structure of an air tube used in theelectronic sphygmomanometer according to the embodiment.

FIG. 13 is a perspective view illustrating another structure of the airtube used in the electronic sphygmomanometer according to theembodiment.

FIG. 14 is a perspective view illustrating yet another structure of theair tube used in the electronic sphygmomanometer according to theembodiment.

FIG. 15 is a cross-sectional view illustrating an anchoring structurefor the air tube used in the electronic sphygmomanometer according tothe embodiment.

FIG. 16 is a first cross-sectional view illustrating an anchoring stepfor the air tube used in the electronic sphygmomanometer according tothe embodiment.

FIG. 17 is a second cross-sectional view illustrating an anchoring stepfor the air tube used in the electronic sphygmomanometer according tothe embodiment.

DETAILED DESCRIPTION OF INVENTION

Hereinafter, an electronic sphygmomanometer according to one or moreembodiments of this invention will be described with reference to thedrawings. When numbers, amounts, and so on are discussed in thefollowing embodiments, it should be noted that unless explicitlymentioned otherwise, the scope of the present invention is notnecessarily limited to those numbers, amounts, and so on. Furthermore,in the case where multiple embodiments are giving hereinafter, it isassumed from the outset that the configurations of the respectiveembodiments can be combined as appropriate unless explicitly mentionedotherwise. In the drawings, identical reference numerals refer toidentical or corresponding elements; there are also cases whereredundant descriptions are omitted.

The present embodiment describes an electronic sphygmomanometer thatcalculates blood pressures through an oscillometric method using theupper arm as a measurement area, and as an example, includes twopressure sensors. Note that the method applied for the blood pressurecalculation is not limited to an oscillometric method.

External View of Electronic Sphygmomanometer 1

FIG. 1 is a diagram illustrating an external view of an electronicsphygmomanometer 1 according to an embodiment of this invention. FIG. 2is a block diagram illustrating the hardware configuration of theelectronic sphygmomanometer according to the embodiment of the presentinvention. As seen in FIGS. 1 and 2, the electronic sphygmomanometer 1includes a main body portion 10, a front cover 11, and a cuff 20 thatcan be wrapped around the upper arm of a measurement subject. The cuff20 includes an air bladder 21. A display unit 40 configured of aliquid-crystal display or the like and an operation unit 41 configuredof multiple switches for accepting instructions from a user (measurementsubject) are disposed on the front cover 11.

In addition to the aforementioned display unit 40 and operation unit 41,the main body portion 10 includes: a CPU (central processing unit) 100for carrying out centralized control of the respective elements andperforming various types of computational processes; a processing memory42 that stores programs, data, and so on for causing the CPU 100 toperform predetermined tasks; a data storage memory 43 for storingmeasured blood pressure data and so on; a power supply 44 for supplyingpower to the various elements of the main body portion 10; and a timer45 that measures the current time and outputs the measured time data tothe CPU 100.

The operation unit 41 includes: a measure/stop switch 41A that acceptsthe input of an instruction for turning the power on or off and acceptsan instruction for starting and stopping measurement; a timer set switch41B manipulated in order to set the timer 45; a memory switch 41C foraccepting an instruction to read out information stored in the memory43, such as blood pressure data, from the memory 43 and display thatinformation in the display unit 40; and arrow switches 41D and 41E foraccepting instructions to raise/lower numbers when setting the timer andmemory numbers when calling information from a memory.

The main body portion 10 further includes a cuff pressure adjustmentmechanism having a pump 51 and an exhaust valve (called simply a “valve”hereinafter) 52. An air system configured of the pump 51, the valve 52,and a first pressure sensor 321 and second pressure sensor 322 fordetecting pressures within the air bladder 21 (cuff pressures) isconnected, via a cuff air tube 31, to the air bladder 21 enclosed withinthe cuff 20.

The main body portion 10 further includes the aforementioned air system,the cuff pressure adjustment mechanism, and a first oscillation circuit331 and second oscillation circuit 332. The cuff pressure adjustmentmechanism includes a pump drive circuit 53 and a valve drive circuit 54,in addition to the pump 51 and the valve 52.

The pump 51 supplies air to the air bladder 21 in order to increase thecuff pressure. The valve 52 is opened/closed in order to discharge orinject air into the air bladder 21. The pump drive circuit 53 controlsthe driving of the pump 51 based on a control signal supplied from theCPU 100. The valve drive circuit 54 controls the opening/closing of thevalve 52 based on a control signal supplied from the CPU 100.

Electrostatic capacitance pressure sensors, for example, are used forthe first pressure sensor 321 and the second pressure sensor 322. Withan electrostatic capacitance pressure sensor, a capacity value changesin accordance with a detected cuff pressure. The first oscillationcircuit 331 and the second oscillation circuit 332 are respectivelyconnected to corresponding pressure sensors, and oscillate based on thecapacity values of the corresponding pressure sensors.

As a result, signals having frequencies based on the capacity values ofthe corresponding pressure sensors (called “frequency signals”hereinafter) are outputted. The outputted frequency signals are suppliedto the CPU 100. The CPU 100 detects a pressure by converting thefrequency signal inputted from the first oscillation circuit 331 or thesecond oscillation circuit 332 into a pressure.

FIG. 3 illustrates the functional configuration of the electronicsphygmomanometer 1 according to the present embodiment. As shown in FIG.3, the CPU 100 includes a pressure adjustment unit 111, a blood pressurecalculation unit 112, a sensor abnormality detection unit 113, arecording unit 114, and a display processing unit 115.

The pressure adjustment unit 111 adjusts the cuff pressure bycontrolling the pump 51 and the valve 52 via the pump drive circuit 53and the valve drive circuit 54 in order to inject/discharge airinto/from the air bladder 21 via the cuff air tube 31.

According to one or more embodiments of the present invention, the bloodpressure calculation unit 112 includes an averaging unit 1121 and avalue abnormality determination unit 1122. The blood pressurecalculation unit 112 detects pulse wave amplitude information based onthe frequency signal inputted from the first oscillation circuit 331 orthe second oscillation circuit 332 (this frequency signal refers to apressure information signal), calculates a systolic blood pressure and adiastolic blood pressure based on the detected pulse wave amplitudeinformation through the oscillometric method, and also calculates thenumber of pulse beats per predetermined amount of time based on thedetected pulse wave amplitude information.

Specifically, as the cuff pressure is gradually increased (or decreased)to a predetermined value by the pressure adjustment unit 111, the pulsewave amplitude information is detected based on the cuff pressureinputted from the first oscillation circuit 331 or the secondoscillation circuit 332, and the systolic blood pressure and thediastolic blood pressure of the measurement subject are calculated basedon the detected pulse wave amplitude information. A known conventionalmethod can be applied in the calculation of the blood pressure and thecalculation of the pulse by the blood pressure calculation unit 112through the oscillometric method.

The sensor abnormality detection unit 113 takes the frequency signalsoutputted from the first oscillation circuit 331 and the secondoscillation circuit 332 as inputs, and detects abnormalities in thefirst pressure sensor 321 and the second pressure sensor 322 byanalyzing the inputted signals.

The recording unit 114 has functionality for reading out data from thememory 43 or writing data into the memory 43. Specifically, therecording unit 114 inputs data outputted from the blood pressurecalculation unit 112, and stores the inputted data (blood pressuremeasurement data) in a predetermined storage region of the memory 43.Furthermore, the recording unit 114 takes the data outputted from thesensor abnormality detection unit 113 as an input, and stored theinputted data (that is, the result of detecting abnormalities in thepressure sensors) in a predetermined storage region of the memory 43. Inaddition, the recording unit 114 reads out measurement data from apredetermined storage region of the memory 43 based on an operation madethrough the memory switch 41C of the operation unit 41, and outputs themeasurement data to the display processing unit 115.

The display processing unit 115 inputs supplied data, converts the datainto a displayable format, and displays the converted data in thedisplay unit 40.

FIG. 3 illustrates only the circuits around the CPU 100 that directlyinput/output to/from the CPU 100.

FIG. 4 illustrates a procedure carried out in a blood pressuremeasurement process according to the present embodiment. The flowchartin FIG. 4 illustrating the stated procedure is stored in advance in amemory 42 as a program, and the blood pressure measurement processillustrated in FIG. 4 is realized by the CPU 100 reading out the programfrom the memory 42 and executing instructions.

First, when the measurement subject manipulates (presses) themeasure/stop switch 41A (step ST1), the CPU 100 resets a working memory(not shown) (ST2).

Next, the first pressure sensor 321 and the second pressure sensor 322are adjusted to 0 mmHg (ST3).

Here, the measurement subject wraps the cuff 20 around the measurementarea (the upper arm) of the measurement subject and wears the cuff 20.When the measurement subject operates (presses) the measure/stop switch41A after wrapping the cuff 20 around the measurement area (step ST4),the pressure adjustment unit 111 outputs control signals to the pumpdrive circuit 53 and the valve drive circuit 54. Based on the controlsignals, the valve drive circuit 54 closes the valve 52, and the pumpdrive circuit 53 drives the pump 51. As a result, the cuff pressure isgradually increased to a predetermined pressure (steps ST5, ST6).

After the cuff 20 has been inflated to the predetermined pressure(“≧predetermined inflation value” in step ST6), the pressure adjustmentunit 111 outputs control signals to the pump drive circuit 53 and thevalve drive circuit 54. Based on the control signals, the pump drivecircuit 53 stops the pump 51, after which the valve drive circuit 54gradually controls the valve 52 so as to open. The cuff pressuregradually decreases as a result (step ST7).

During this pressure reduction process, the blood pressure calculationunit 112 detects the pulse wave amplitude information based on thefrequency signal outputted from the first oscillation circuit 331 or thesecond oscillation circuit 332, or in other words, based on a cuffpressure signal detected by the first pressure sensor 321 or the secondpressure sensor 322; a predetermined computation is then carried out onthe detected pulse wave amplitude information. The systolic bloodpressure and the diastolic blood pressure are calculated through thiscomputation (steps ST8, ST9). The pulse wave amplitude informationexpresses a component of the change in volume of an artery in themeasurement area, and is included in the detected cuff pressure signal.The computations during the calculation of the blood pressure by theblood pressure calculation unit 112 are carried out in accordance withthe characteristics of the pressure sensors. Note that the bloodpressure measurement is not limited to being carried out during thepressure reduction process, and may instead be carried out during theprocess of increasing the pressure (step ST5).

When the systolic blood pressure and diastolic blood pressure have beencalculated and determined (YES in step ST9), the pressure adjustmentunit 111 fully opens the valve 52 via the valve drive circuit 54, andquickly discharges the air within the cuff 20 (step ST10).

The blood pressure data calculated by the blood pressure calculationunit 112 is outputted to the display processing unit 115 and therecording unit 114. The display processing unit 115 takes the bloodpressure data as its input, and displays that data in the display unit40 (step ST11). Meanwhile, the recording unit 114 takes the bloodpressure data as its input, and stores that data in a predeterminedstorage region of the memory 43 in association with time data inputtedfrom the timer 45 (step ST12).

Note that the blood pressure calculation unit 112 can also calculate thenumber of pulse beats based on the detected pulse wave amplitudeinformation. The calculated number of pulse beats is displayed in thedisplay unit 40 by the display processing unit 115, and is stored in thememory 43 in association with the blood pressure data by the recordingunit 114.

Note that the operations described thus far are the same as thoseperformed by conventional sphygmomanometers. With conventionalelectronic sphygmomanometers, users have been unable to determinewhether the pressure sensors, which are of utmost importance whencalculating blood pressures, are operating normally or havemalfunctioned. Thus, for example, in the case where a blood pressuremeasurement value differs greatly (for example, a difference of morethan 10 mmHg) from a normal value (for example, a measurement valueobtained the previous day, a measurement value obtained at a hospital,or the like), it is not known whether that value comes from actualbiological information of the measurement subject or if the pressuresensor has merely malfunctioned; this has caused concern on the part ofthe user.

Accordingly, the electronic sphygmomanometer 1 according to the presentembodiment includes the first pressure sensor 321 and the secondpressure sensor 322, and calculates blood pressures by taking theaverage value of the cuff pressures detected by these pressure sensors.As a result, even in the case where fluctuations have occurred in thedetection accuracy of one of the pressure sensors due to changes overtime, the reliability of blood pressure measurement values can beimproved by calculating the average value.

Structure In Which Pressure Sensors Are Disposed

Next, a structure for disposing the first pressure sensor 321 and thesecond pressure sensor 322 will be described with reference to FIGS. 5through 7. FIG. 5 is a perspective view illustrating the internalstructure of the electronic sphygmomanometer 1 according to the presentembodiment, where the front cover 11 has been removed from the main bodyportion 10. The electronic sphygmomanometer 1 according to presentembodiment has a structure in which, when the electronicsphygmomanometer 1 is placed on a mount surface B, the front cover 11 issloped.

In order to make it easier for the user (measurement subject) to viewthe display unit 40 and to make it easier to operate the operation unit41 provided in the front cover 11, the front cover 11 is sloped (the Ydirection shown in FIG. 5) so that the side facing the user (measurementsubject) (the front side; the side indicated as H1 in FIG. 5) is lowerand the rear side (the side indicated as H2 in FIG. 5) is higher. Forthis reason, an internal circuit board 12 housed internally is alsodisposed parallel to the front cover 11, and is thus sloped so that thefront side (the side indicated as H1 in FIG. 5) is lower and the rearside (the side indicated as H2 in FIG. 5) is higher.

As shown in FIG. 5, the first pressure sensor 321 and the secondpressure sensor 322 are disposed on a front surface side 12 a of theinternal circuit board 12, which corresponds to a first main surface,along the horizontal direction (the X direction in FIG. 5) that isorthogonal to the direction in which the front cover 11 of theelectronic sphygmomanometer 1 slopes. In the present embodiment, forexample, the first pressure sensor 321 and the second pressure sensor322 are disposed along a direction orthogonal to the direction in whichthe front cover 11 of the electronic sphygmomanometer 1 slopes. FIGS. 6and 7 are diagrams viewing the internal circuit board 12 from a rearsurface side, serving as a second main surface that is on the oppositeside as the first main surface. In addition, FIG. 6 illustrates a statein which a pressure sensor air tube 500 is not attached to the firstpressure sensor 321 and the second pressure sensor 322, whereas FIG. 7illustrates a state in which the pressure sensor air tube 500 isattached to the first pressure sensor 321 and the second pressure sensor322.

As shown in FIG. 6, a first air port 327 of the first pressure sensor321 and a second air port 328 of the second pressure sensor 322 aredisposed, at a predetermined distance (L1) from each other, on the rearsurface side of the internal circuit board 12 so as to protrude. Inaddition, the first oscillation circuit is formed on a rear surface 12 bof the internal circuit board 12 in a position in the periphery of thefirst air port 327, and a first shielding plate 323 for protecting thefirst oscillation circuit is attached upon the rear surface 12 b of theinternal circuit board 12. A first opening 325 for exposing the firstair port 327 is provided in the first shielding plate 323. Apredetermined gap is formed between the first shielding plate 323 andthe rear surface of the internal circuit board 12.

Likewise, the second oscillation circuit is formed on the rear surface12 b of the internal circuit board 12 in a position in the periphery ofthe second air port 328, and a second shielding plate 324 for protectingthe second oscillation circuit is attached upon the rear surface 12 b ofthe internal circuit board 12. A second opening 326 for exposing thesecond air port 328 is provided in the second shielding plate 324. Apredetermined gap is formed between the second shielding plate 324 andthe rear surface of the internal circuit board 12.

As shown in FIG. 7, during actual use, the pressure sensor air tube 500is attached to the first air port 327 of the first pressure sensor 321and the second air port 328 of the second pressure sensor 322. Abranching air tube 401 that branches from the cuff air tube 31 isconnected to the pressure sensor air tube 500.

The pressure sensor air tube 500 includes: a first air port connectionhead 501 that is connected to the first air port 327; a second air portconnection head 502 that is connected to the second air port 328; afirst connection tube 503 that is provided in the first air portconnection head 501 and that is connected to the branching air tube 401;and a second connection tube 504 that connects the first air portconnection head 501 and the second air port connection head 502. Anelastomer (rubber, a thermoplastic elastomer) or the like is used as thematerial for the pressure sensor air tube 500.

According to the structure in which the pressure sensors are disposed inthe present embodiment, stress resulting when the load of the pressuresensor air tube 500 is applied to the pressure sensors can bedistributed approximately uniformly between the first pressure sensor321 and the second pressure sensor 322. For example, in the case wherethe two pressure sensors are arranged and disposed in the verticaldirection (the direction orthogonal to the X direction in FIG. 5), theload from the pressure sensor air tube 500 is applied to the firstpressure sensor 321 and the second pressure sensor 322 in a non-uniformmanner due to the slope of the internal circuit board 12.

However, in the present embodiment, the first pressure sensor 321 andthe second pressure sensor 322 are disposed, on the front surface side12 a that serves as the first main surface of the internal circuit board12, following the horizontal direction (the X direction FIG. 5) that isorthogonal to the direction in which the internal circuit board 12slopes; as a result, the first pressure sensor 321 and the secondpressure sensor 322 are disposed having the same height position fromthe mount surface B.

Accordingly, as shown in FIG. 7, when the pressure sensor air tube 500is attached to the first pressure sensor 321 and the second pressuresensor 322, the load of the pressure sensor air tube 500 is distributedapproximately uniformly between the first pressure sensor 321 and thesecond pressure sensor 322, which makes it possible to make the stressapplied to the pressure sensors approximately equal.

As a result, it is possible to improve the reliability of blood pressuremeasurement values obtained by an electronic sphygmomanometer that usestwo pressure sensors, or the first pressure sensor 321 and the secondpressure sensor 322. Note that in order to distribute the load of thepressure sensor air tube 500 more equally between the first pressuresensor 321 and the second pressure sensor 322, according to one or moreembodiments of the present invention, as shown in FIG. 8, the firstconnection tube 503 to which the branching air tube 401 is connected isdisposed in a position that is centered on the first air port connectionhead 501 and the second air port connection head 502.

Details of Structure of Pressure Sensor Air Tube 500

Next, details of the structure of the pressure sensor air tube will bedescribed with reference to FIGS. 9 through 14. First, details of thestructure of the pressure sensor air tube 500 illustrated in FIG. 7 willbe described with reference to FIGS. 9 and 10.

As described above, the pressure sensor air tube 500 includes: the firstair port connection head 501 that is connected to the first air port327; the second air port connection head 502 that is connected to thesecond air port 328; the first connection tube 503 that is provided inthe first air port connection head 501 and that is connected to thebranching air tube 401; and the second connection tube 504 that connectsthe first air port connection head 501 and the second air portconnection head 502. An elastomer (rubber, a thermoplastic elastomer) orthe like is used as the material for the pressure sensor air tube 500.

The outer diameter of the first connection tube 503 is represented byDb, whereas the inner diameter is represented by Dc. As a specificexample of the dimensions, the outer diameter (Db) is approximately 4.5mm, whereas the inner diameter (Dc) is approximately 2 mm Meanwhile, theouter diameter of the second connection tube 504 is represented by Da,whereas the inner diameter is represented by Dc, which is the same aswith the first connection tube 503. As a specific example of thedimension, the outer diameter (Da) is approximately 4 mm.

In this manner, the thickness of the material of the second connectiontube 504 is set to be lower than the thickness of the material of thefirst connection tube 503, and thus the second connection tube 504 ismore flexible than the first connection tube 503. As a result, even iferror has occurred in the structural dimensions of the pressure sensorair tube 500, that is, in the distance between the first air port 327and the second air port 328 (L1; see FIG. 6), the second connection tube504 can extend/contract, which makes it possible to absorb the error inthe structural dimensions of the pressure sensor air tube 500.

Accordingly, in the case where the pressure sensor air tube 500 has beenattached to the first pressure sensor 321 and the second pressure sensor322, the second connection tube 504 provides a stress reduction function(Sf), which makes it possible to reduce unnecessary stress (compressionstress/pulling stress) from being applied to the first pressure sensor321 and the second pressure sensor 322. As a result, it is possible toimprove the reliability of blood pressure measurement values obtained byan electronic sphygmomanometer that uses two pressure sensors, or thefirst pressure sensor 321 and the second pressure sensor 322.

Details of Structures of Pressure Sensor Air Tube 500A/500B

Next, details of the structure of a pressure sensor air tube 500Aserving as a variation will be described with reference to FIG. 11. FIG.11 is a cross-sectional view corresponding to the X-X line in FIG. 9. Inthe pressure sensor air tube 500A, the outer diameter of the firstconnection tube 503 and the outer diameter of a second connection tube510 have the same outer diameter dimension (Db), but the inner diameterdimension (Dd) of the second connection tube 510 is set to be greaterthan the inner diameter dimension (Dc) of the first connection tube 503.As a specific example of the dimension, the inner diameter dimension(Dd) of the second connection tube 510 is approximately 2.5 mm.

Employing this configuration also makes the thickness of the material ofthe second connection tube 510 lower than the thickness of the materialof the first connection tube 503, which makes it possible to provide asimilar stress reduction function (Sf) as the pressure sensor air tube500. Note that with a pressure sensor air tube 500B shown in FIG. 12, asecond connection tube 520 is, unlike the second connection tube 510illustrated in FIG. 11, configured of a different member that is moreflexible than the first connection tube 503, the first air portconnection head 501, and the second air port connection head 502;however, the dimensional relationships are the same as with the secondconnection tube 510.

Details of Structure of Pressure Sensor Air Tube 500C

Next, details of the structure of a pressure sensor air tube 500Cserving as a variation will be described with reference to FIG. 13. Thispressure sensor air tube 500C employs a tube having a bulging structureas a second connection tube 530. By employing such a structure, thesecond connection tube 530 is capable of extending/contracting, whichmakes it possible to provide a similar stress reduction function (Sf) asthe pressure sensor air tube 500.

Details of Structure of Pressure Sensor Air Tube 500D

Next, details of the structure of a pressure sensor air tube 500Dserving as a variation will be described with reference to FIG. 14. Thispressure sensor air tube 500D employs a tube having an accordionstructure as a second connection tube 540. By employing such astructure, the second connection tube 540 is capable ofextending/contracting, which makes it possible to provide a similarstress reduction function (St) as the pressure sensor air tube 500.

Anchoring Structure For Pressure Sensor Air Tube 500

Next, an anchoring structure for the pressure sensor air tube 500 willbe described with reference to FIG. 9 and FIGS. 15 through 17. Note thatthe anchoring structures for the pressure sensor air tubes 500A through500D illustrated in FIGS. 11 through 14 are the same as the anchoringstructure for the pressure sensor air tube 500. In addition, in FIG. 15,the front surface side of the internal circuit board 12 is illustratedas being on the bottom, whereas the rear surface side is illustrated asbeing on the top.

As shown in FIG. 9, protruding members 505 that engage with the innersurface side of the first shielding plate 323 within the first opening325 provided in the first shielding plate 323 when the first air port327 is connected thereto are formed on the outside surface of the firstair port connection head 501 in the pressure sensor air tube 500. In thepresent embodiment, the protruding members 505 are provided in a totalof two locations that are opposite to each other by 180°.

Likewise, protruding members 505 that engage with the inner surface sideof the second shielding plate 324 within the second opening 326 providedin the second shielding plate 324 when the second air port 328 isconnected thereto are formed on the outside surface of the second airport connection head 502 in the pressure sensor air tube 500. In thepresent embodiment, the protruding members 505 are provided in a totalof two locations that are opposite to each other by 180°.

As shown in FIG. 15, the same anchoring structure for the pressuresensor air tube 500 is employed for the first air port connection head501 and the second air port connection head 502, and therefore thefollowing will describe only the anchoring structure of the first airport connection head 501.

By inserting the first air port connection head 501 into the first airport 327 through the first opening 325 provided in the first shieldingplate 323, the protruding members 505 provided on the outside surface ofthe first air port connection head 501 pass over the first shieldingplate 323 while elastically deforming and reach a position on the innerside of the first shielding plate 323. Through this, it is possible toanchor the first air port connection head 501 to the first shieldingplate 323. As a result, the first air port connection head 501 can beprevented from pulling out from the first air port 327.

Here, the anchoring of the first air port connection head 501 to thefirst shielding plate 323 during the assembly of the electronicsphygmomanometer 1 will be described with reference to FIGS. 16 and 17.As shown in FIG. 16, the first air port connection head 501 (pressuresensor air tube) is positioned in advance in a predetermined position onthe main body portion 10.

Next, the internal circuit board 12 is positioned in a predeterminedposition on the main body portion 10 from above the first air portconnection head 501. At this time, it is not possible for a worker tocheck the first air port connection head 501 visually. It can be saidthat because the first air port connection head 501 has an elasticforce, the first air port connection head 501 can be anchored by pushingthe first air port 327 into the first air port connection head 501.However, it is also thought that if the position of the first air port327 has shifted, the internal circuit board 12 will be pushed againstthe main body portion 10 with the first air port connection head 501 ina bent state.

However, according to the present embodiment, the protruding members 505are provided, and in the case where the first air port 327 has beenpushed into the first air port connection head 501, the protrudingmembers 505 pass over the first shielding plate 323 while elasticallydeforming and reach a position on the inner side of the first shieldingplate 323; accordingly, a worker can feel the first air port 327 lockinto place when the protruding members 505 return to their originalforms. Through this, even though the worker cannot see that the firstair port 327 has been connected to the first air port connection head501, the worker can still confirm this connection.

Although a structure in which protruding members are provided in the airport connection heads and the protruding members engage with theshielding plates is employed in the present embodiment, embodiments ofthe present invention are not limited to this structure. For example, adedicated plate for engaging with the protruding members can be providedabove the internal circuit board 12. Alternatively, as a variation, astructure in which a direct engagement region is provided in theinternal circuit board 12 and the air port connection heads are engagedwith this engagement region can also be employed.

Furthermore, although the present embodiment describes a case where theprotruding members are provided in two locations on the outside surfacesof the air port connection heads, it should be noted that in the casewhere priority is placed on the worker obtaining a sense of theprotruding members locking into place upon returning to their originalforms as described above, the configuration may be such where theprotruding members are provided in only a single location on the outsidesurfaces of the air port connection heads.

In addition, although the present embodiment describes a case where thefirst air port connection head 501 and the second air port connectionhead 502 are provided so that the two pressure sensors can be connectedto the pressure sensor air tube 500, the configuration of the presentembodiment with respect to the anchoring structure for the pressuresensor air tube can be employed for a single pressure sensor as well.

Although the aforementioned embodiment describes a case where the firstpressure sensor 321 and the second pressure sensor 322 are disposed onthe front surface side 12 a of the internal circuit board 12 and thepressure sensor air tube 500 is disposed on the rear surface side 12 bof the internal circuit board 12, it should be noted that the sameeffects can be achieved in the case where the first pressure sensor 321and the second pressure sensor 322 are disposed on the rear side surface12 b of the internal circuit board 12 and the pressure sensor air tube500 is disposed on the front surface side 12 a of the internal circuitboard 12.

Furthermore, although the aforementioned embodiment describes a casewhere two pressure sensors are used, the configuration according to theembodiment can also be employed in the case where three or more pressuresensors are used.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

REFERENCE NUMERALS LIST

1 electronic sphygmomanometer

10 main body portion

11 front cover

12 internal circuit board

12 a front surface side

20 cuff

21 air bladder

31 cuff air tube

40 display unit

41 operation unit

41A measure/stop switch

41B timer set switch

41C memory switch

41D, 41E arrow switch

42, 43 memory

44 power supply

45 timer

51 pump

52 valve

53 pump drive circuit

54 valve drive circuit

100 CPU (Central Processing Unit)

111 pressure adjustment unit

112 blood pressure calculation unit

1121 averaging unit

1122 value abnormality determination unit

113 sensor abnormality detection unit

114 recording unit

115 display processing unit

321 first pressure sensor

322 second pressure sensor

323 first shielding plate

324 second shielding plate

325 first opening

326 second opening

327 first air port

331 first oscillation circuit

332 second oscillation circuit

401 branching air tube

500, 500A, 500B, 500C, 500D pressure sensor air tube

501 first air port connection head

502 second air port connection head

503 first connection tube

504, 510, 520, 530, 540 second connection tube

505 protruding member

The invention claimed is:
 1. An electronic sphygmomanometer comprising:a cuff that is worn on a measurement area; an inflation and deflationunit that adjusts a pressure applied to the cuff; a pressure detectingunit, comprising a pressure sensor, that detects a cuff pressure withinthe cuff based on pressure information outputted from the pressuresensor; and a blood pressure calculation unit that calculates a bloodpressure based on a change in the cuff pressure detected by the pressuredetecting unit, wherein the pressure sensor is disposed upon a firstmain surface of an internal circuit board, wherein the pressure sensorcomprises an air port that protrudes on a second main surface that is onan opposite side of the internal circuit board as the first mainsurface; wherein a pressure sensor air tube is connected to the airport, wherein a branching air tube that branches from a cuff air tubeconnected to the cuff is connected to the pressure sensor air tube,wherein the pressure sensor air tube comprises an air port connectionhead connected to the air port, and wherein an engagement region thatengages the air port connection head with the internal circuit board isprovided between the air port connection head and the internal circuitboard.
 2. The electronic sphygmomanometer according to claim 1, whereinthe internal circuit board comprises a shielding plate that is disposeda predetermined distance from the second main surface and in which isprovided an opening that exposes the air port on a side of the secondmain surface, and wherein the air port connection head comprises aprotruding member, serving as the engagement region, that engages withan inner surface side of the shielding plate at the opening when anoutside surface of the air port connection head is connected to the airport.
 3. The electronic sphygmomanometer according to claim 2, whereinno less than two of the protruding members are provided in the outsidesurface of the air port connection head.
 4. The electronicsphygmomanometer according to claim 2, wherein a first pressure sensorand a second pressure sensor are provided as the pressure sensors,wherein the pressure detecting unit detects the cuff pressure within thecuff based on the pressure information outputted from the first pressuresensor and the second pressure sensor, wherein a first air port for thefirst pressure sensor and a second air port for the second pressuresensor are provided as the air port, wherein the internal circuit boardcomprises a first shielding plate that is disposed a predetermineddistance from the second main surface and in which is provided a firstopening that exposes the first air port on the side of the second mainsurface, and a second shielding plate that is disposed a predetermineddistance from the second main surface and in which is provided a secondopening that exposes the second air port on the side of the second mainsurface, wherein the pressure sensor air tube comprises a first air portconnection head connected to the first air port and a second air portconnection head connected to the second air port, wherein the first airport connection head comprises the protruding member that engages withan inner surface side of the first shielding plate at the first openingwhen the outside surface of the first air port connection head isconnected to the first air port; and wherein the second air portconnection head comprises the protruding member that engages with aninner surface side of the second shielding plate at the second openingwhen the outside surface of the second air port connection head isconnected to the second air port.
 5. The electronic sphygmomanometeraccording to claim 4, wherein no less than two of the protruding membersare provided in the outside surface of the air port connection head.